import sys
from PyQt5.QtCore import Qt
from PyQt5.QtWidgets import (QWidget,QLCDNumber,QSlider,
                             QVBoxLayout,QApplication)


class Example(QWidget):

    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        lcd = QLCDNumber(self)
        sld = QSlider(Qt.Horizontal,self)

        vbox = QVBoxLayout()
        vbox.addWidget(lcd)
        vbox.addWidget(sld)
        self.setLayout(vbox)
        sld.valueChanged.connect(lcd.display)

        self.setGeometry(300,300,300,300)
        self.setWindowTitle('signal & slot')
        self.show()

    def keyPressEvent(self,e):
        if e.key() == Qt.Key_Escape:
            self.close()

if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())
